Users interact with HVAC systems through user interfaces. The most common user interface employed today is the thermostat. The most basic thermostats feature one or more dials, switches or levers and allow users to set temperatures. More elaborate thermostats feature a liquid crystal display (LCD) screen, perhaps even of the touchscreen variety, and allow users to program their HVAC systems for automatic temperature settings, configure and maintain their HVAC systems and records of historical operation data, allowing the users to gauge the performance and efficiency of their HVAC systems.
Thermostats necessarily include both temperature sensors and control circuitry within their housings. Some user interfaces do not qualify as thermostats, because while they communicate with temperature sensors and control circuitry, they do not include both within their housings.